In recent years, autonomous driving assistance systems have been newly proposed which provide a vehicle traveling mode other than manual traveling in which a vehicle travels in response to driving operations by a user. The autonomous driving assistance system causes a vehicle to perform some or all of driving operations that are to be performed by a user, thus assisting a user to drive the vehicle. The autonomous driving control system detects, as necessary, the current location of a vehicle, a lane where the vehicle travels, the locations of other vehicles around, etc. and autonomously performs vehicle control of a steering wheel, a driving source, a brake, etc. so that the vehicle travels along a preset route.
What is important here to cause the autonomous driving assistance system to appropriately perform driving assistance is to cause the vehicle to correctly understand the environment surrounding the vehicle. Examples of means for causing the vehicle to understand the surrounding environment include information detected by cameras or sensors mounted on the vehicle, and information acquired through communication with external serves or other vehicles. For example, in the technology proposed in Japanese Patent Application Publication No. 2013-544695 (JP 2013-544695 A), when a vehicle travels through a section (hereinafter referred to as an autonomous driving difficult section), such as a merging section or a road work section, where the vehicle has difficulty in traveling by using autonomous driving, the vehicle distributes information about the traveled autonomous driving difficult section to other nearby vehicles, thus providing a warning about the autonomous driving difficult section to the other vehicles that have received the information. It is further proposed that after the warning is provided, the travel route is changed to a route that avoids the autonomous driving difficult section, or the driving mode is changed in whole or in part from autonomous driving to manual driving.